fix: handle pure Python packages in cibuildwheel workflow

- Build pure Python packages (leann-core, leann) with standard build tool
- Only use cibuildwheel for C extension packages (leann-backend-hnsw, leann-backend-diskann)
- Build pure Python packages only once on ubuntu-latest
- Add Python setup for building pure packages
- Add package listing step for debugging

.github/workflows/build-cibuildwheel.yml

@@ -24,16 +24,21 @@ jobs:
           ref: ${{ inputs.ref }}
           submodules: recursive
       
-      # Build each package separately in our monorepo
-      - name: Build leann-core wheels
-        uses: pypa/cibuildwheel@v2.16.2
+      - name: Setup Python
+        uses: actions/setup-python@v5
         with:
-          package-dir: packages/leann-core
-          output-dir: wheelhouse
-        env:
-          CIBW_BUILD: cp39-* cp310-* cp311-* cp312-*
-          CIBW_SKIP: "*-win32 *-manylinux_i686 pp*"
-          # Pure Python package, no special requirements
+          python-version: '3.11'  # Version for building pure Python packages
+      
+      # Build each package separately in our monorepo
+      - name: Build pure Python packages (leann-core, leann)
+        if: matrix.os == 'ubuntu-latest'  # Only build once, they're platform-independent
+        run: |
+          # Install build tools
+          python -m pip install --upgrade pip build
+          
+          # Build pure Python packages
+          python -m build packages/leann-core --outdir wheelhouse/
+          python -m build packages/leann --outdir wheelhouse/
       
       - name: Build leann-backend-hnsw wheels  
         uses: pypa/cibuildwheel@v2.16.2
@@ -85,15 +90,10 @@ jobs:
           CIBW_TEST_REQUIRES: leann-core numpy
           CIBW_TEST_COMMAND: python -c "import leann_backend_diskann"
       
-      - name: Build leann meta-package
-        uses: pypa/cibuildwheel@v2.16.2
-        with:
-          package-dir: packages/leann
-          output-dir: wheelhouse
-        env:
-          CIBW_BUILD: cp39-* cp310-* cp311-* cp312-*
-          CIBW_SKIP: "*-win32 *-manylinux_i686 pp*"
-          # Pure Python meta-package
+      - name: List built packages
+        run: |
+          echo "📦 Built packages:"
+          ls -la wheelhouse/
       
       - uses: actions/upload-artifact@v4
         with: